Catalysis mechanism and catalyst design of diamond growth
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I. INTRODUCTION
AFTER Pauling[1] described the atom state of heavy elements in the periodic table with the mixture of two properly selected Russell–Sanders models, i.e., hybridization, Yu described the atom state of all elements with the hybridization of properly selected h (head) state and t (tail) state between the base state and the highest excitation state, and established “the empirical electron theory of solid and molecule,”[2] i.e., EET theory. Yu employs the bond-length-difference (BLD) method[2] to theoretically build the valence electron structure of crystal and molecule by ascertaining the hybrid state of all atoms and calculating out the covalent electron distribution among these atoms with known lattice constants. However, the practical state of the atoms has to be ascertained by character parameters. In the early 1990s, Cheng proposed improved Thomas– Fermi–Dirac (TFD) theory.[3] Cheng pointed out that the normal TFD model fails to solve the problems of the boundary of condensed substance. Some errors seem to exist in the model regarding the treatment of atom conditions, especially of the boundary condition between atoms in solid. Cheng suggests that the electron density on the contact surface of atoms in solid must be continuous, and this is the quantum condition of wave function continuity and the criterion for the forming and generating of alloy. In Reference 4, the boundary condition of electron movement, i.e., “the electron density being equal on the contacting surfaces of atoms,” in the improved TFD theory was applied to the (111)g // (110)a crystal sample in Yu’s EET. As expected, the result shows that the electron density of the (111)g crystal plane of austenite is equal to that of the (110)a plane of martensite. This continuity condition can confine the selecting condition in Yu’s theory and, therefore, clears up the uncertainty of parameters to be selected in EET. ZHILIN LIU, Professor and Vice-President, ZHILIN LI, Associate Professor, and ZHENGUO SUN, Professor, are with the Department of Materials Science and Engineering, Liaoning Institute of Technology, Jinzhou, Liaoning 121001, People’s Republic of China. Manuscript submitted October 30, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS A
In this article, we employ EET and its BLD method to calculate the valence electron structures of diamond and the catalysts Mn, Co, and Ni of artificial diamond. On this basis, we employ the boundary condition of electron movement in the improved TFD theory to decide the continuity of the electron density of the interface and find that of diamond growth interface is continuous. With the valence electron structure analysis together with geometry factor analysis, we explain the growth process of diamond under catalysis condition and the catalysis mechanism of Mn, Co, and Ni. Furthermore, we advance the electron criterion of catalysis behavior of elements, which can be the basis of catalysts search and design. II. CRYSTAL STRUCTURE OF Mn3C, Co3C, Ni3C, AND DIAMOND A. Crystal Structure of Mn3C, Co3C, and N
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